Batteries for LED calcs, revisited

[burkhard]

Looks neat, but I don't get it. What does that offer over a more conventional aftermarket NiMH 3-pack offered by several sources on eBay and elsewhere?
The NiMH:
1. Has similar (or higher) energy capacity to LiPo.
2. Drops right in using the OEM HP battery contacts in the compartment. No special jumpers or adapters.
3. Recharges with the HP charger (or via a special USB cable sold nowadays). No special off-board charging rig-up required.
4. Price is similar to this LiPo.
5. Unlike LiPo, NiMH don't (often) burst into flame.

Maybe I'm wrong or missing something, but I se LiPo batteries as a good way to maximize energy density in odd available shapes (wide and flat, log and thing, &c.) That's great for a new design of a super-compact phone, but if you have an existing device designed to fit AA form factor batteries, why go LiPolymer? What is it providing over off-the-shelf NiMH solutions?